So, today was maintenance day on the hydraulic system, thanks again for the help with the return filter! Stuck hydraulic return filter I’m servicing the hydraulic return filter on a Cat 311B, S/N 8GR00401. I don’t know when the last time this filter was serviced. Following the service instructions I have released any pressure in the tank, removed the filter cover and released the pressure in the filter canister. Next you’re... HeavyEquipmentForums For reference I last sampled the hydraulic oil at 5980 hrs, machine now has 6040 hrs. The results from that sample were good (posted in this thread- HeavyEquipmentForums ) All was going well after I got the new filter installed, I had stored the machine for the winter with the boom/stick extended to retract the cylinders. I cycled each function slowly as I had also changed the pilot filter. I then stopped in the hydraulic level check position (level within the normal range). When I was done I parked the machine with the stick extended again; I happened to open the hydraulic compartment again and now I see the start of milky oil in the sight gauge…. Aw, ****!! I had noticed that the hydraulic oil fill plug was a few turns loose, I can only assume I forgot to tighten it at the end of last season. Otherwise, there are no other known leaks. So, where do I go from here? Drain and keep flushing the system with new oil? Filter cart? Cat 311B, s/n 8GR00401.
Looks like no one else is excited about this repair, either! I am going to look at the oil in the tank tonight, the stratification in the sight glass has me optimisticly hoping I could drain the majority of the water/emulsion off the bottom of the tank… doubtful but we will see. Failing that, it looks like a complete flush/system clean out is in order. I am not sure I can or want to tackle that myself…. I was quoted a similar price by the mobile Cat dealer service and by a hydraulic repair company. However, the hydraulic repair place wants to truck the excavator to their shop and not do it in the field. Opinions on this?
Predictably, no miracle occurred… with that said, I have two questions. First in looking at the machine it looks like there is one return to tank line that services the main valve bank and also a pilot line supply/return. If I took the return lines and extended them to route to a drum of waste oil and then cleaned the tank out and filled with clean oil could I cycle clean oil through the system and force the contaminated oil out into the waste drum? Second, is cleaning out this type of contaminated oil something that could be reasonably completed in a field service call?
What did the Cat house and the local shop quote? How much to haul to local shop and back?
Both quoted around $4500. Of that price the local hydraulic shop had $3100 in materials and labor and $1500 in transport. Cat had $2800 in parts, $1200 in labor and $500 in mileage. Some of the online reviews for the independent hydraulic shop are not good… I have not used this place before. (My typical go-to hydraulic place said that they don’t work on complete machines). As of now my plan is to go with Cat as they have a name to stand behind and I have had good service from this dealer before.
Have you tried opening the drain from the hydraulic oil tank, let the oil run for a couple of minutes and and see what comes out.? Make sure if you go with Cat that they give you documentary evidence from oil analysis results, etc, proving that your system is clean and free from water. They should also include the numbers for the ISO 4406 Cleanliness Code as well.
I did tonight, yes. I got some clean water from the drain then steady milky oil. I also spun off the two brand new hydraulic filters (15 minutes run time) and they were full of milky crap. This is the explanation and plan for the repair from Cat service- “Tech said it could take up to 3 flushes depending on how milky your oil is. He can get away with using the current filter for the flushes and will use one replacement filter after the last flush. We also quoted 4 hours of labor but he thinks he could get it done in about 3 so long as he doesn’t run into any issues.” Thoughts?
A barrel of 10W chevron hydraulic oil costs me $800. You could buy 5 barrels for $4500 with money left over. Slew the machine so it is crossing the tracks, then take the skid plate off under the hydraulic tank. Take the step plate off the top of the tank, and any other covers that get in the way. Release the pressure from the tank by slowly loosening the fill cap. There is a drain plug in the bottom of the tank, situate a barrel and funnel under it, and pull the plug. If you want more fluid pull one of the plugs in the suction line to the pump. If you are ok with a mess you can loosen lines on the cylinders while it is running and flush fluid out there too. I would just drain and fill it, and run the machine for a while, maybe 10 hours, and monitor the fluid. If it is still milky, repeat. For $4500 you could also buy a filter cart and pump the tank through that. I am told that there are filters that work to remove the water. I don't have firsthand experience with this, somebody else might.
Why couldn't a guy buy a water separator filter, Tee-In to the Pilot filter feed and run the oil throught a needle valve into the filter and out of it into a tank return. The needle valve would be to slow down the oil so as not to over-pressurize the filter housing. It would be like a kidney loop. Not sure who sells a water separator filter, but someone must. You would have to run all functions to get all the oil through the filter multiple passes. I did something similar to clean a transmission circuit and it worked fine. Simon C
The filter and housing for 5 micron to clean the transmission cost me $125 plus a couple pieces of push on hose. Simon C
Here is one I installed on a Chev 2500 Truck to clean the transmission oil. The oil sample after had 1/17th the particle count. It worked for me. Simon C
Thanks for all the replies! I really appreciate the suggestions. I have a very basic knowledge of the hydraulic system so I don’t know that I am savvy enough to be adding filters or hooking up a filter cart. I know I could handle simply dumping the tank and refilling it to cycle the contaminated oil through… is it possible to re-route the return line away from the tank and push new clean oil from the tank through the system or am I showing my ignorance here?
No, not really. Theoretically you could, but if your machine is set up anything like mine, it would be a significant undertaking. Considering that you feel that modifying the filters is above your pay grade, I wouldn't try it. I don't know how you would fill the reservoir fast enough to keep up with the pump anyway. I don't know the specs but I suppose you will pump that reservoir dry in about 20 seconds.
I think that I would like to explore this option to continue to clean up the system after I have the bulk contamination removed. If anyone is able to suggest an appropriate filter base and filter for water cleanup that would be very helpful. I tried finding something on the Donaldson website but there are so many options it’s hard to determine what I need. Even if I need to change out the filter repeatedly it seems like it would help. Once I have the filter selected I’ll be back to seek advise on how to plumb it into the system. Alternatively maybe I can replace one of the existing filters with one that also removes water? Cat filters 093-7521 and 5I-8670 are the ones used on this machine.
I prefer to remove the water from the oil, then change the oil to replace the depleted additives. So get the water from 5% to .5%, then change the oil and get it to .25%, instead of changing it multiple times, or flushing it line by line and cylinder by cylinder. Bubbling dry air through oil will remove most of the water, and can be set up to be repeated many times to mix the oil in the system back to the tank to dry the whole system with repeated working and drying. There are other methods like centrifuge, vacuum dehydration, boiling that work better with the oil off the machine. Or filters could work, but they have a very limited water capacity, so that's not fast or easy either.
Thanks for the insight! I assume you introduce the air through an aquarium bubbler or similar?
Water removal filters only remove approx. 1 teaspoon of water per filter and cost around $50.00 each so that isn't really an economical option. Water contaminated oil is a common problem in all hydraulic equipment and there is no known quick solution. Flush, refill operate the machine and change filters is the standard procedure and that's why Cat and most everyone else charges what they do. In the past I have often saved hydraulic oil from other machines, ran it through a filter system and then used it to flush contaminated systems but even then it takes a lot of time and effort. Centrifuges, dehydrators ect are all very expensive, this is something I have looked at for years and have come to the conclusion that if there was an easier, more economical way others would be doing it already.
Torq force? That's cheap. Like less than my cost cheap. List price is about $1700 a drum.
Yes. $822.25, to be exact, delivered to my shop. One (very small) perk to civilization; not having to pay the dogsled teams to haul oil out . . . ?
I used a refrigerator compressor, with an air filter on the intake and the output going through a steel 3/16" brake line that was inside a hose to allow the exhaust air to warm the incoming air, had the hose come off the top but turn and slant down and away to drain condensation out. Also warmed the oil at the same time, but that was winter, might not need the heat in summer or for an hour after use.
Interesting, I happen to have an old fridge compressor around. If I set something like this up and used it in the machine tank after every time I used the machine would that help dry out the water remaining in the system after I flushed it out a few times? Do you have a picture of your setup?
I used to look after a fleet of bucket trucks. One of them was a "bare-hand truck" it was used to work on the transmission lines. Most were 287KV if I remember correctly. The hydraulic oil had to have a dielectric test done every three months. If it failed the tank had to be drained and refilled then cycle every hydraulic cylinder three times. Then drain refill again and cycle the cylinders a total of three times then send out a sample of the new oil for a dielectric test. It seemed to fail every third test and took 200 litres to flush the system. The solution was to install a sealed filler cap and desiccant filter for a vent in one of the spare threaded holes in the hydraulic tank. This seemed to resolve the problem. The filter came from Altec Aerials. It was a black plastic cylinder with a clear plastic cap that had a red plastic pin that would pop up when the desiccant was full.
I don't have a picture of the setup, I hooked it up after running the machine, or ran it overnight with heat. Just the rubber hose over the tube, no hose clamps because there's no pressure. I'd think it would work better to remove the gross contamination, THEN change the oil. Like I said, use air to get from 5% to .5% water, then change the oil to get another half of the water out. Instead of changing the oil to get from 5 to 2.5% and then trying to get down to .25% with air.
Does anyone know of a desiccant breather with a 2 to 5 psi regulator built into it? Preferably built out of steel or aluminum?
So, I decided to flush the system thoroughly, with the help of @Monkeywithawrench (thanks again!). Total of about 85 gallons of oil and all new filters. After 5 hours of runtime I pulled an oil sample; today I got the results back (see attached). No water was noted in the sample and the cleanliness still seems good. Hopefully that puts this issue behind me!
ISO 16/12 is better than the standard for new/fill oils which is 16/13. A couple of filter changes and you'll be back down to the 15/11 where you were before.
Thanks Nige. What interval would you suggest before the next filter change?
If it was me I would have put a High Efficiency clean-out filter in it for 50 hours after changing the oil. What is the Part Number of the standard filter.?
093-7521 is the hydraulic filter, 5I-8670 is the pilot and 126-2081 is the return. (Those are the numbers on the filters I just put on).
Use a 179-9806 on the return in place of the 126-2081. The other two filter Part Numbers can remain the same. Don't run it more than 100 hours before changing.
Got it, thanks Nige. I’ll pick up one of those filters this week and install it.
With hydraulic oil as clean as yours TBH you could use the 179-9806 permanently as a replacement. Change every 500 hours or prior to that if the filter indicates as plugged.